Combination-sensitive neurons are selectively responsive to specific combinations of different stimulus features. They play an important role in sensory processing, but the synaptic mechanisms that establish their unique response properties have not yet been explored. The jamming avoidance response (JAR) in the fish Gymnarchus requires a joint analysis of electric field amplitude and phase modulation (AM and PM), each of which are processed in separate pathways that converge onto combination-sensitive neurons in the torus semicircularis. This study will address the synaptic mechanisms that result in non-linear responses to combinations of AM and PM. Specific aims are to: (1) record postsynaptic potentials in toral neurons while manipulating AM, PM, and combinations of both; (2) analyze the morphology and projection patterns of toral neurons in relation to combination sensitivity; (3) assess the role of individual toral neurons in controlling the JAR; and (4) test hypotheses on the mechanisms driving non-linearities using immunocytochemistry and pharmacological manipulation. The proposed research will provide insight into how combination-sensitive neurons are able to extract behaviorally relevant information from multiple stimulus features.